Effect of Bacillus subtilis as a probiotic on protein, lipid content, and trypsin and chymotrypsin enzymes in rainbow trout biometry (Oncorhynchus mykiss)

Abstract

This study investigated the effect of Bacillus subtilis IS02 as a probiotic bacterium in four different treatment conditions, namely T1 (no probiotic), T2 (106), T3 (107), and T4 (108) cfu/g of B. subtilis IS02 in the diet of rainbow trout for 30 days, on the protein content, lipid content, trypsin and chymotrypsin enzyme activity, and the bioassay. The protein content and lipid content were measured using the Kjeldahl and Soxhlet methods, respectively.T4 had the highest amount of measured protein (25.30%) while T1 had the lowest amount (15.90). The T4 treatment had a significant effect (P value = 0.001) on improving the protein content as well as the trypsin and chymotrypsin enzyme activity. In contrast, there was no significant difference in terms of the weight gain and specific growth rate between the treatments. Additionally, the results showed that the T3 treatment had a significant effect on increasing the protein content of the carcass, although the effect was not significant in relation to the lipid content. B. subtilis IS02 in a concentration range of 107–108 cfu/g could be employed to improve the protein productive value, trypsin and chymotrypsin enzyme activity, and protein content of the carcass.